Archiving e-Invoices on Poland’s KSeF Portal under the 2026 E-Invoicing Mandate

Introduction
Poland is embarking on a nationwide shift to electronic invoicing, centered on the Krajowy System e-Faktur (KSeF) – the National e-Invoicing System. From 2026, virtually all B2B invoices in Poland must be issued and processed through KSeF, replacing traditional paper and PDF invoices. A key aspect of this system is the archiving of e-invoices on a government-run portal, which promises to relieve businesses from some record-keeping burdens. This article explains how e-invoicing in Poland will work once the mandate is in effect, focusing on the archiving requirements and processes in KSeF, as well as the overall e-invoice workflow, compliance obligations, and technical details (formats, APIs, retention periods). We’ll also trace past developments, outline the current status as of late 2025, and look at future changes to expect. [polishtax.com], [polishtax.com]

Background: Poland’s Journey to Mandatory E-Invoicing (KSeF)

Poland introduced KSeF as a voluntary platform in 2022, laying the groundwork for a phased mandatory rollout. Below is a timeline of key developments leading up to the mandate:

Archiving and Retention of E-Invoices in KSeF

One of the hallmark features of KSeF is automatic archiving of all e-invoices on the central government platform. When an invoice is processed through KSeF, it is not only cleared for tax purposes but also stored in a secure government database for long-term access. Here’s how archiving works under the new system and what businesses need to know: [polishtax.com]

10-Year Central Archive: Every invoice submitted to KSeF is archived by the system for 10 years counted from the end of the year of issuance. For example, an invoice issued in March 2026 will be kept in the KSeF repository until the end of 2036. These e-invoices remain accessible online to both the issuer and the recipient throughout that period. The Ministry of Finance has emphasized that an invoice in KSeF “will always be available” to both parties, and cannot be lost or destroyed in the interim. In other words, KSeF provides a guaranteed backup for all structured invoices – eliminating concerns about losing invoices due to local system crashes, file corruption, or physical damage to paper archives. [vatupdate.com], [forvismazars.com] [forvismazars.com], [polishtax.com]
No Duplicate Archiving Required: Because KSeF retains the official record, taxpayers using KSeF are not required to store their issued or received e-invoices separately in their own archive for the first 10 years. Polish regulations were adjusted so that the obligation to archive invoices can be met by the KSeF system itself. Unlike in the past where companies kept paper folders or digital backups of every invoice, now the KSeF portal serves as the primary archive. There is also no need to issue duplicate copies of an invoice for archiving purposes – the concept of a “copy” or “duplicate” invoice becomes obsolete since the one e-invoice in KSeF is the single source of truth accessible to all relevant parties. For instance, if a customer misplaces the invoice file sent to them, the issuer can simply direct them to KSeF (or resend the same cleared invoice with its KSeF ID) rather than creating a formally labeled “duplicate” invoice. [forvismazars.com]
Coverage of All Invoices (Sales and Purchases): The KSeF archiving applies to all structured invoices, regardless of how they were delivered or who generated them. This means your sales invoices and your purchase invoices from other companies are all stored in your KSeF account. If you are a buyer receiving an invoice via KSeF, that invoice lands in your part of the KSeF system and is archived for you as well. KSeF thus acts like a ledger of all a company’s outbound and inbound invoices. Importantly, the archived invoices in KSeF fulfill record-keeping requirements for both VAT and income tax purposes. Tax auditors or the company’s accounting team can rely on the KSeF repository to retrieve any invoice within the 10-year window for VAT audits, corporate income tax reviews, etc. [vatupdate.com]
Retention Laws and Business Responsibilities: Poland’s tax law generally requires businesses to retain invoices for 5 years after the end of the fiscal year in which they were issued (this aligns with the statute of limitations for tax liabilities). KSeF’s 10-year archive comfortably exceeds this minimum. In most cases, using KSeF means a company has met its legal retention obligation without doing anything extra, since the tax authority itself keeps the invoices for at least 10 years (which covers the 5-year requirement plus a safety margin). However, KSeF’s archive “does not fully replace taxpayers in this process”. There are scenarios where longer retention might be needed. For example, proof of purchase of a non-residential building might need to be kept beyond 10 years due to extended tax depreciation or inspection periods. If an invoice relates to a transaction with a longer statutory document retention period (e.g. certain real-estate or investment records), the taxpayer must ensure they separately archive those invoices beyond KSeF’s 10-year limit to remain compliant. In practice, this might mean exporting and safekeeping certain invoices before KSeF purges them after year 10. [basware.com] [vatupdate.com]
Business Continuity and Best Practice: Even though the law doesn’t require maintaining a parallel archive, many advisors recommend that businesses still implement their own archive or backup for e-invoices. Reasons include ensuring data control and accessibility (e.g., having invoices in your own system for quick internal access or analytics) and safeguarding against any unexpected issues (for instance, if a business loses access to KSeF due to credential problems or if the government policies change). There’s also the consideration of what happens after 10 years – companies may want records beyond the decade (for example, for long-term trend analysis or in case of very late tax queries). While KSeF greatly reduces the archiving burden, prudent companies will likely download and store copies of cleared invoices in their ERP or document management systems as a backup measure. [basware.com], [aprosoftwa…utions.com] [aprosoftwa…utions.com]
KSeF as an Archive for Small Businesses: On the flip side, KSeF’s archiving feature is a boon especially for small entities that lacked sophisticated archiving solutions. A small business that previously kept invoices in shoe-boxes or scattered PDF files can rely on KSeF to automatically store all their invoices in one place with government-grade security. Even if a business discontinues operations, the invoices remain in KSeF and can be accessed if needed years later. This was illustrated by cases where former entrepreneurs struggled to retrieve old invoices stored on obsolete hard drives after closing their business – a situation KSeF’s centralized archive would prevent. Thus, KSeF archiving not only meets legal requirements but also provides a reliable repository that outlives the business itself, ensuring historical invoice data isn’t lost. [vatupdate.com]

In essence, Poland’s KSeF turns archiving into a centralized, automated service. For active compliance, a company just needs to use KSeF; the system will handle preservation of the invoices. Businesses should be mindful of edge cases requiring longer storage, but for the vast majority of transactions, KSeF’s 10-year archive means one less compliance headache – invoices “will always be available” to both seller and buyer on the portal. The archiving by the tax authority covers the critical period in which most tax audits or queries would arise, and it applies equally to all invoices processed, whether they are outgoing or incoming. [forvismazars.com] [vatupdate.com]

Briefing document & Podcast: Poland E-Invoicing, E-Reporting and KSeF Mandate – VATupdate